Modular vertebral stabilizer

ABSTRACT

A stabilizer device for the spinal column, comprising a first body ( 2 ) and a second body ( 2 ) adapted to be mutually connected by a rod-like element ( 5 ), the first and second bodies ( 2 ) being adapted to be fitted around first and second pedicle screws ( 3 ), which are adapted to be inserted in turn in two mutually adjacent vertebrae, the first and second bodies ( 2 ) being fixable on the pedicle screws ( 3 ), the first and second bodies ( 2 ) being fork-shaped and adapted to accommodate locking means ( 20 ), the locking means ( 20 ) being adapted to pass from a position for accommodating the pedicle screw ( 3 ) to a position for locking the pedicle screw ( 3 ) within the fork-shaped body ( 2 ).

TECHNICAL FIELD

The present invention relates to a modular vertebral stabilizer. Moreparticularly, the invention relates to a modular vertebral stabilizerthat is adapted to mutually connect at least two adjacent vertebrae byusing at least two connecting elements which can prevent or allow somecertain limited movement to the vertebrae.

BACKGROUND ART

As is known, many pathologies related to the functionality of the spinalcolumn are treated by total or partial immobilization, particularly witha technique known as intervertebral arthrodesis, with the aid ofconnection means and/or with the addition of portions of bone tissuewhich join such adjacent vertebrae.

Vertebral stabilization devices of the static and dynamic types areknown in the art and have a screw that is adapted to be connected to avertebra and rigid elements or elements that have a limited mobility,which have two ends which are jointly connected to the two screwsconnected to two adjacent vertebrae.

In particular, a dynamic stabilizing device, i.e., capable of allowingrelative movement between the vertebrae, is disclosed in EP 0 669 109.This vertebral stabilizer comprises a spacing body, which is resistantto compression and is adapted to transfer forces between two screwsimplanted in the respective vertebrae, and a tensioning cord, which isconnected between the two screws described above and passes in aninternal longitudinal cavity obtained in the spacing body.

However, this stabilizer has a drawback, due to the fact that it isdirectly assembled locally on the spinal column after inserting thescrews in the vertebrae, with open surgery in a space that is close tothe vertebra. Therefore, the surgical procedure that allows to use suchstabilization structure is highly invasive, since it is necessary tocreate close to the vertebra enough space to perform the various stepsof assembly, with considerable difficulty for the surgeon, who mustarrange and assemble each individual element directly on the vertebra.

Moreover, the stabilizer described above does not allow a transverseconnection between screws mounted on different vertebrae in order totransmit forces in a diagonal direction with respect to the axis of thespinal column.

Further, the tensioning cord must be threaded in the spacing body, andthis require a higher skill effort for the surgeon.

Moreover, the surgeon may need a stabilizer that has both static anddynamic portions, i.e., he may have to create a hybrid stabilizer, inwhich the portions can be chosen by the surgeon according to thecharacteristics of the pathology.

Known types of stabilizer do not allow to create a stabilizer of thehybrid type.

WO2007/060534 A2 in the name of this same Applicant as the presentinvention, discloses a vertebral stabilizer of the dynamic modular type,which is adapted to be assembled separately from the spinal column andthen fitted onto the spinal column in a few seconds.

However, the known type of stabilizer device is unable to adapt to anglevariations with which the pedicle screws might be fitted within thevertebrae, and therefore, if the positioning of such pedicle screws isnot performed, in two adjacent vertebrae, with the same angle, thesurgeon encounters difficulties in fitting the stabilizer device fittedover the head of the pedicle screws.

DISCLOSURE OF THE INVENTION

The aim of the present invention is to provide a device for stabilizingthe spinal column which allows connection between adjacent vertebrae,allowing different angles between pedicle screws inserted in adjacentvertebrae.

Within this aim, an object of the present invention is to provide astabilizer device that can be assembled separately from the spinalcolumn and then fitted onto the spinal column with reduced invasivenessfor the patient.

Another object of the present invention is to provide a spinal columnstabilizer device that is modular, allowing therefore to provide ahybrid stabilizer device, i.e., a device that is static at one end anddynamic at the opposite end.

Another object of the present invention is to provide a stabilizerdevice that is highly reliable, relatively simple to provide and atcompetitive costs.

This aim and these and other objects that will become better apparenthereinafter are achieved by a stabilizer device for the spinal column,comprising a first body and a second body adapted to be mutuallyconnected by a rod-like element, said first and second bodies beingadapted to be fitted around first and second pedicle screws, which areadapted to be inserted in turn in two mutually adjacent vertebrae, saidfirst and second bodies being fixable on said pedicle screws,characterized in that said first and second bodies are fork-shaped andadapted to accommodate locking means, said locking means being adaptedto pass from a position for accommodating said pedicle screw to aposition for locking said pedicle screw within said fork-shaped body.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages of the invention will becomebetter apparent from the following detailed description of somepreferred but not exclusive embodiments of the device according to thepresent invention, illustrated by way of non-limiting example in theaccompanying drawings, wherein:

FIG. 1 is an exploded perspective view of a stabilizer device accordingto the present invention;

FIG. 2 is a top plan view of the stabilizer device according to thepresent invention, in a first embodiment, in an unassembledconfiguration around a pedicle screw;

FIG. 3 is a top plan view of the stabilizer device according to thepresent invention, in the first embodiment, in an assembledconfiguration around the pedicle screw;

FIG. 4 is a top plan view of the stabilizer device according to thepresent invention, in a second embodiment, in an unassembledconfiguration around the pedicle screw;

FIG. 5 is a top plan view of the stabilizer device according to thepresent invention, in the second embodiment, in an assembledconfiguration around the pedicle screw.

With reference to the figures, a stabilizer device according to thepresent invention, generally designated by the reference numeral 1,comprises a fork-shaped body 2, which is adapted to engage a pediclescrew 3 designed to be inserted in a vertebra.

The fork-shaped body 2 is provided with a portion 4 which blends withthe circular portion that forms the fork, the portion 4 having a seatthat is adapted to accommodate a rod-like element 5.

Conveniently, the portion 4 has at least one hole 6 that is adapted toallow the insertion of stabilizing means, which are convenientlyconstituted for example by a cord 7 which is connected to a secondfork-shaped body 2 arranged at the opposite end of the rod-like element5.

Substantially, the stabilizer device according to the invention hasfirst and second fork-shaped bodies 2, which are adapted to be connectedby the rod-like element 5 and to engage respectively two pedicle screws3 arranged respectively in two adjacent vertebrae which are adapted tobe mutually stabilized.

The pedicle screws are conveniently headless and cannulated, so thatthey can be screwed into the vertebrae.

Conveniently, the rod-like element 5 is provided with a pair of mutuallyopposite lateral recesses 8, which are adapted to accommodate the cord 7which must be fastened around the rod-like element 5.

Conveniently, the two ends of the cord 7 are provided with respectiveengagement means 9, which are adapted to allow tensioning of the cord 7.

Conveniently, the engagement means 9 can be provided for example withone end of the cord provided with a set of teeth and the opposite endprovided with a receptacle, like a hose clamp.

In this manner, the surgeon can perform, separately from the spinalcolumn, a fastening of the cord 7 around the rod-like element 5 andthen, once the stabilizer device has been assembled, said device can befitted around the pedicle screws 3 that are already accommodated in theholes provided in the vertebrae to be coupled in a stabilized manner.

Conveniently, the rod-like element 5 can be of the rigid type, in whichcase the presence of the cord 7 is not necessary, or of the elastictype, with which the cord 7 is therefore associated.

In a second embodiment of the device according to the invention, shownin FIGS. 4 and 5, the fork-shaped body 2 is provided in such a manner asto mate with a corresponding fork-shaped body 2 that is arranged in adiametrically opposite position with respect to the pedicle screw 3. Inthis case, the mating of the two fork-shaped bodies provides a completedisk-like element, which surrounds the pedicle screw 3 completely.

Therefore, differently from the first embodiment, in which thefork-shaped body 2 has a substantially U-shaped internal contour, thebody 2 of the second embodiment has a semicircular internal contour,which is adapted to surround half of the pedicle screw 3, the other halfof the screw being surrounded by the corresponding fork-shaped body 2arranged diametrically opposite the first body.

In this manner it is possible to mutually connect more than two adjacentvertebrae and it is also possible to provide a hybrid modular stabilizerdevice, i.e., a device that is partially static and partially dynamic,depending on whether the rod-like element 5 is of the rigid or elastictype.

It is in fact possible to connect to each other first and secondadjacent vertebrae by using a rigid rod-like element and connect thesecond vertebra and a third vertebra, which is adjacent to the secondvertebra, by using an elastic rod-like element. In this manner a hybridstabilizer device is obtained.

Conveniently, the mating of two fork-shaped bodies 2 arranged mutuallyopposite with respect to the pedicle screw 3, as shown in FIGS. 4 and 5,occurs by way of the presence of mating means 15 and 16 provided at eachend of the fork.

Substantially, the mating means 15 are constituted for example by aprotruding pin provided with a tooth 18, while the mating means 16 havea seat that is adapted to accommodate the pin 15 and the correspondingtooth 18.

Each fork-shaped body therefore has a mating means 15 and a mating means16 which are adapted to mate complementarily with similar means on theopposite fork-shaped body 2.

Other mating means are of course possible, so long as they are capableof ensuring a stable mating of the two fork-shaped bodies which aremutually opposite with respect to the pedicle screw 3.

The stabilizer device according to the invention, assembled away fromthe spinal column, is then inserted under the skin of the patient sothat the distal fork-shaped body 2 engages the distal pedicle screw 3and then the proximal fork-shaped body 2 fits on the pedicle screw 3.

In the first embodiment, locking of the fork-shaped body 2 is providedby way of locking means, such as for example an open annular element 20,which is C-shaped and inserted within the U-shaped portion of thefork-shaped body 2.

Such annular element is adapted to rotate freely within said U-shapedportion, so that it can be turned around the pedicle screw 3, as shownin FIGS. 3, so as to lock the fork-shaped body 2 around the pediclescrew 3.

The rotation of the annular element 20 can be performed thanks to thepresence of a pair of holes 21 arranged at the face of the fork-shapedbody 2, which allows the insertion of a tool that allows to turn theannular element 20.

In practice it has been found that the stabilizer device according tothe present invention fully achieves the intended aim and objects, sinceit allows to be assembled away from the spinal column, allows to adaptto different implantation angles of the pedicle screws within thevertebrae, and allows to provide hybrid structures with rigid portionsand elastic portions.

The stabilizer device thus conceived is susceptible of numerousmodifications and variations, all of which are within the scope of theappended claims; all the details may further be replaced with othertechnically equivalent elements.

In practice, the materials used, as well as the contingent shapes anddimensions, may be any according to requirements and to the state of theart.

The disclosures in Italian Patent Application No. MI2008A002240 fromwhich this application claims priority are incorporated herein byreference.

Where technical features mentioned in any claim are followed byreference signs, those reference signs have been included for the solepurpose of increasing the intelligibility of the claims and accordingly,such reference signs do not have any limiting effect on theinterpretation of each element identified by way of example by suchreference signs.

1. A stabilizer device for the spinal column, comprising a first bodyand a second body adapted to be mutually connected by a rod-likeelement, said first and second bodies being adapted to be fitted aroundfirst and second pedicle screws, which are adapted to be inserted inturn in two mutually adjacent vertebrae said first and second bodiesbeing fixable on said pedicle screws, characterized in that said firstand second bodies are forked shaped and adapted to accommodate lockingmeans, said locking means being adapted to pass from a position foraccommodating said pedicle screw to a position for locking said pediclescrew within said fork-shaped body.
 2. The stabilizer device accordingto claim 1, characterized in that said locking means comprise asubstantially C-shaped annular element, which is adapted to rotatefreely within said fork-shaped body and to pass from a position foraccommodating said pedicle screw to a position for locking said pediclescrew when said C-shaped element is rotated about said pedicle screw. 3.The stabilizer device according to claim 1, characterized in that saidfirst and second fork-shaped bodies have a protruding portion thatblends with said body to accommodate said rod-like element.
 4. Thestabilizer device according to claim 1, wherein said rod-like element isrigid.
 5. The stabilizer device according to claim 1, wherein saidrod-like element is elastic.
 6. The stabilizer device according to claim1, wherein said rod-like element is provided with a pair of mutuallyopposite lateral recesses to accommodate a retention cord that isadapted to be gripped around said rod-like element.
 7. The stabilizerdevice according to claim 1, characterized in that at least one of saidfirst and second fork-shaped bodies is provided with means for matingwith a respective similar fork-shaped body.
 8. The stabilizer deviceaccording to claim 7, characterized in that said mating means allow tomate two mutually identical fork-shaped bodies around said pediclescrew.
 9. The stabilizer device according to claim 1, characterized inthat said fork-shaped body is provided with at least one hole on itsupper surface which is adapted to allow the insertion of a tool for therotation of said C-shaped annular element.
 10. The stabilizer deviceaccording to claim 1, characterized in that said protruding portion ofsaid fork-shaped body is provided with at least one hole for theinsertion of said cord or of a grub screw that is adapted to lock saidrod-like element within said protruding portion.
 11. An element forfixing to a pedicle screw, comprising a body adapted to be fitted aroundsaid pedicle screw, characterized in that said body is fork-shaped andaccommodates locking means which are adapted to pass from a position foraccommodating said pedicle screw within said body to a position forlocking said pedicle screw within said body.
 12. The fixing elementaccording to claim 1, characterized in that said locking means comprisesC-shaped open annular element, which is adapted to rotate within saidfork-shaped body and to pass from a position for accommodating saidpedicle screw to a position for locking said pedicle screw when saidopen annular element is locked around said pedicle screw.
 13. The fixingelement according to claim 11, characterized in that said fork shapedbody is provided with means for mutual mating with a respective similarfork-shaped body, for the mating of said fork-shaped bodies around saidpedicle screw.
 14. The fixing element according to claim 11,characterized in that said fork-shaped body contains a protrudingportion provided with at least one hole for the passage of a retentioncord or of a grub screw that is adapted to lock a rod-like elementwithin said protruding portion.